The present invention relates to a vacuum chamber provided with a vacuum vessel containing inside a processing chamber, where a substrate-like sample such as a semiconductor wafer is processed in a reduced pressure state, and particularly the present invention relates to one provided with a transfer unit for transferring the sample under atmospheric pressure, and a unit for making this sample fit with the predetermined position.
The vacuum chamber such as the above is one for processing a sample by reducing pressure of a processing chamber arranged inside the vacuum vessel to the predetermined vacuum degree. In such a chamber, in general, a sample such as a wafer is transferred to the processing chamber piece by piece, therefore there is connected a transfer vessel in which the wafer is transferred the inside of a transfer chamber, whose inside is depressurized similarly, in communication with the vacuum vessel, as well as there is arranged with a transfer machine for transferring the sample at the inside of a transfer chamber, for example, a robot having an arm for transfer.
In addition, in such a chamber, the sample is stored in a cassette under atmosphere nearly adjusted to atmospheric pressure, and carried to the vacuum chamber, and the sample is transferred between the processing chamber and the cassette, in a state installed and connected in this chamber. Therefore, a transfer machine (the robot) for transferring the sample is arranged at each of a region in the chamber set to the predetermined vacuum degree, and a region set to atmospheric pressure.
Further, between the vacuum region containing the above vacuum transfer chamber where the sample is transferred under vacuum, and the region where the sample is transferred under atmospheric pressure, there is a unit called a lock chamber for adjusting pressure of inside the by pressurization or depressurization, between atmospheric pressure and pressure of the predetermined vacuum degree, by connecting these. This lock chamber is a space inside a vessel where pressure is changed by sealing, after carrying-in or carrying-out the sample stored in the inside in each of a state under atmospheric pressure and a state under vacuum. That is, the lock chamber is an interface to connect the region of the vacuum side and the region of the atmospheric side.
Incidentally, it is required that the transfer robot (atmospheric transfer robot) at the region of the atmospheric side steers the sample toward a specific direction for processing inside the processing chamber, when the sample is taken out from the inside of the cassette, transferred to the processing chamber, and subjected to processing. For example, in the case of cutting out a semiconductor device from a semiconductor wafer after completion of the processing, it is necessary to perform the cutting along a direction of specific crystal of the semiconductor. One of the reasons for this is because the case of cutting out in a direction not along the crystal direction results in generation of damage or crack in the semiconductor device, and decrease in yield.
Therefore, in a conventional vacuum chamber, there is provided with a unit for alignment of a sample in a specific direction. For example, there has been performed formation of a notched part at the predetermined outer edge part of a circular sample, in advance, and detection of the notched part of the sample, by an alignment unit, before the sample taken out from the cassette is carried into the lock chamber, as well as alignment of the sample in a specific direction by rotating the sample. By detection of V-notch position by performing alignment about a plurality of samples in this specific direction, in the alignment unit, and by performing alignment, persistent processing results can be obtained and reproducibility of sample processing can be enhanced.
In such an alignment unit, eccentricity and position of a specific part of the sample, which is transferred and mounted on the unit, are detected; size of eccentricity of the center and position of the notched part are detected with a specific sensor, for example, a laser-type line sensor or the like, by rotating the sample; the notched part is steered in a specific direction by rotating the sample; as well as the sample is moved in a horizontal direction and center eccentricity is corrected. In this way, in the alignment unit, detection and adjustment of eccentricity of the sample and the specific direction are performed.
Further, there is known such one that detects size of eccentricity of a sample in the alignment unit, and adjusts position of a transfer robot based on this, and eccentricity is corrected, in receiving the sample from the alignment unit. As an example of such conventional technology, there is known one disclosed in JP-A-10-173022. In this present conventional technology, the alignment unit only steers the sample in a specific direction by detecting position of the notched part, and by rotating the sample, and adjustment of eccentricity is adjusted in receiving the sample by entering a robot arm downward of the sample which is retained on the alignment unit.